The biological behavior of the mesotheliomas can be predicted by their gross look, those shape and structures

solitary, discrete masses are generally benign, whereas those, which grow diffusely, are usually malignant.
Mesothelioma is a tumor emerging from mesothelial lining of serous cavities, most often covering of lungs (the pleural cavity) , rarely, in coverings of abdomen (peritoneal cavity) and covering the heart (pericardial sac).

They are two types benign and malignant.

MesotheliomaBenign or Solitary.
Benign or solitary can also called by pleural fibroma. Exposures of asbestos play no role on the e etiology of benign mesothelioma. Entirely it consists of a solitary, circumscribed, small, firm mass and generally less than one inch in diameter. Dense fibrous tissues can be seen by cut the surface. The tumor is composed by predominantly of collage fibers and reticulin with interspersed fibroblasts. Unusual, mesothelial lined clefts are seen in the tumor. Benign mesothelioma causes tumor is associated with systemic syndrome of osteoarthropathy or hypoglycemia. Removal of the tumor is generally curative.

MesotheliomaMalignant or diffuse.
It is a highly malignant tumor with high mortality and it is rare. Usually after 20 to 40 years exposure to asbestos the tumor can be detected. Almost 90 percent of malignant mesotheliomas are asbestos related.

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